It is known to provide glass plates with a polymer frame that surrounds the edge of the plate. This is typically accomplished by placing the glass plate between two mold halves, in which are formed mould cavities corresponding to the desired frame profile. The mold halves are closed and the mold cavities are then filled with a melted thermoplastic polymer or polymer reaction system to form the frame profile. Processes of this type are used to a significant extent and are described, for example, in U.S. Pat. Nos. 4,584,155, 4,688,752, 4,732,553 and 4,830,804; EP 0,333,538, DE 1,945,291, DE 3,920,925, and CA 1,234,660. Processes of this type require complicated molds which due to their considerable costs, render these processes too expensive for use on small batches.
According to another known process, frame-like profiles or frame parts made from a polymer are shaped onto the glass plate by an extrusion process. Here again, it is possible to use reaction systems, such as moisture-hardening polyurethane systems or thermoplastic polymers, to form the profile. Processes of this type are shown, for example, in the following U.S. Pat. Nos. 4,571,278, 5,062,248, 4,933,032, 5,095,669 and 5,108,526, and European Patent Applications 0,479,677, 0,494,824, 0,524,060, 0,524,092, 0,531,201 and 0,537,067. In these processes, the polymer strand is extruded through an extrusion die and placed on the top surface of the glass plate along the circumference.
It has also been proposed to produce a glass plate with a polymer frame by placing the glass plate on a mold bed, which in the edge region of the glass plate engages the lower surface of the plate over and beyond the glass plate circumference, thus forming an extension of the glass plate surface. With the aid of an extrusion die, a profile strand can then be extruded on the glass plate edge which projects beyond the circumference and which is bounded by the mold face (see, e.g., DE 4,232,554). Thus, an L-shaped polymer frame can be provided on the edge of the glass plate, with one part of the L-shape being provided on the top surface of the plate while the other portion of the L-shape is positioned on the outer main surface, i.e. on the outside edge of the glass plate, where it terminates flush with the bottom of the glass plate surface.
There is a need for an improved process for the production of glass plates having a polymer frame shaped on the edges thereof on at least two sides, i.e., on at least the top surface of the plate and the circumferential edge, wherein the process can economically be used for small production batches. The present invention proposes a new process and apparatus which satisfies this need.